The present invention relates to a method for the manufacture of packing containers from tubular, flexible packing material through repeated flattening, sealing and cutting of the packing material tube during the successive substantially vertically downward movement of the same.
The invention also relates to an arrangement for the realization of the method, this arrangement including guiding devices for the packing material tube, co-operating jaws for transverse pressing together and sealing of the tube, and a fill pipe.
Packing containers for milk or other, in particular liquid, foodstuffs are manufactured generally from laminated, flexible material which comprises layers of paper and thermoplastics. A known packing container is formed by successive conversion of a laminate web to tubular form while it is fed through the packing machine. In operation, the web's two longitudinal edges are joined and sealed together in a liquid-tight manner. The tube so formed is moved substantially vertically downwards through the machine at the same time as the contents are furnished via a fill pipe introduced into the upper open end of the tube and extending downwards inside the tube. At the lower end of the tube the machine is provied with reciprocating processing jaws co-operating with one another, which compress the passing material tube at regular intervals so that transverse, flattened zones are produced wherein the walls of the material tube are sealed to one another in a liquid-tight manner. The transverse sealing of the material tube is taking place below the level of the contents and the tube is thus converted to coherent, substantially cushion-shaped packing containers which are completely filled with contents. After the cushion-shaped packing containers have been separated from one another through cuts in the transverse sealing zones, a final form-processing takes place so that the packing containers obtain the desired, for example parallelepipedic shape.
During the flattening of the packing material tube as well as the subsequent form-processing for converting the cushion-shaped packing containers to parallelepipedic shape, the contents are used as an internal holder-up or "mandrel" in the packing container. That is to say the contents generate the internal back pressure which is necessary for making possible the forming of the packing container without undesirable deformation.
The principle of using of the contents as a holder-up in the forming process has worked excellently up to now, since the packing containers have been manufactured so as to be completely filled with incompressible liquid contents, that is to say without air space. If packing containers with air space or headspace are to be manufactured, the contents do not produce the same well-defined and stable back pressure over the whole surface of the packing container and this increases the risk of creasing or other deformations. The technique of manufacture described above has proved less appropriate up to now, for the manufacture of packing containers of the partially filled type.
For corresponding reasons it has not been possible to use the method for other than liquid contents, since the filling of solid particles does not produce the desired, uniform internal back pressure and creates problems with regard to the forming as well as the sealing of packing containers.
It is an object of the present invention to provide a method which allows an accurate proportioning of the quantity of contents into each packing container and which makes it possible to fill the container with solid particles (e.g., pieces of fruit etc.) together with liquid contents or separately from the liquid contents.
It is a further object of the present invention to provide a method which, without appreciable complications, can be utilized in existing packing machines of the type mentioned in the introduction.
These and other objects have been achieved in accordance with the method of the present invention wherein a sealed off part of the packing material tube is pressurized by the feeding of a gaseous pressure medium, whereupon the flattening of the tube within a limited, transverse region takes place against the effect of the internal pressure.
It is also an object of the present invention to provide an apparatus for the realization of the above-mentioned method, this apparatus being simple and reliable in operation and capable of being combined with known types of packing machines.
These and other objects have been achieved in accordance with the apparatus of the present invention wheren a bottom part of the packing material tube is sealed off by a sealing device located in the tube.
The method and the apparatus in accordance with the invention provide a number of advantages inasmuch as they overcome the above-mentioned disadvantages and make it possible to make use of known principles of package forming for the manufacture of packing containers which are only partially filled with contents. The volume of contents in each individual packing container can be regulated with great accuracy, and the filling of fluids as well as solid particles or combinations thereof is possible. By choosing an appropriate pressure medium which is not harmful to the product the method can be utilized for all types of contents occuring in practice and in aseptic as well as non-aseptic manufacture.